Using in vitro protein labelling techniques tubulin and actin present in the soluble pool and in microtubules and microfilaments in brain tissue will be compared by peptide mapping. Brain actin, which has been isolated in high yield and high purity, will be compared to muscle actin by peptide mapping, native and denaturing isoelectric focusing and acrylamide gel electrophoresis, electron microscopic examiniation of assembled filaments, interaction with muscle myosin, spectroscopic properties and immunochemical techniques. Studies on the mechanism of action of nerve growth factor in the induction of neurite outgrowth in dorsal root ganglia will be continued. Specifically, the effects of cyclic AMP and nerve growth factor on different populations of cells in the ganglia will be evaluated with respect to the time of origin of the cellular population. BIBLIOGRAPHIC REFERENCES: Mizel, S.B. and Bamburg, J.R. (1975). Studies on the Action of Nerve Growth Factor. II. Neurotubule Protein Levels During Neurite Outgrowth. Neurobiology 5, 283-290. Mizel, S.B. and Bamburg, J.R. (1976). Studies on the Action of Nerve Growth Factor. I. Characterization of a New in vitro Culture System for Dorsal Root and Symphathetic Ganglia. Develop. Biol. (In press).